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troperville

Use whichever one you're comfortable with.
First come, first served. Don't change the spelling in someone else's writing; this will just lead to edit warring.
If there's strong national ties to the page in question, it's okay to standardi(s/z)e to one spelling. For instance, it's okay to change "colour" to "color" on Eagleland, and it's okay to change "program" to "programme" on British Brevity. The same goes for work pages.
Create redirects for titles with multiple accepted spellings. This makes the page searchable for both styles. Mixing styles in a title doesn't usually make much sense, though.

For comparison, here's the policy

towards this on The Other Wiki.

alternative title(s): American And British English; U After O Except In America; American And Commonwealth Spellings

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